Light Deflection with Torsion Effects Caused by a Spinning Cosmic String

TL;DR

This paper calculates how light bends around a spinning cosmic string considering torsion effects within Einstein-Cartan gravity, revealing that the string's spin and torsion influence the deflection angle.

Contribution

It introduces a new geometrical approach to compute light deflection caused by spinning cosmic strings with torsion in Einstein-Cartan theory.

Findings

Light deflection is affected by the string's intrinsic spin.

Torsion influences the deflection angle.

The method applies the Gauss-Bonnet theorem to optical geometry.

Abstract

Using a new geometrical method introduced by Werner, we find the deflection angle in the weak limit approximation by a spinning cosmic string in the context of the Einstein-Cartan (EC) theory of gravity. We begin by adopting the String-Randers optical metric, then we apply the Gauss-Bonnet theorem to the optical geometry and derive the leading terms of the deflection angle in the equatorial plane. Calculations shows that light deflection is affected by the intrinsic spin of the cosmic string and torsion.